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Relationship Between Cross-Section and Velocity of Flow

What factors contribute to the rate of flow in blood vessels? The rate of movement of blood through vessels depends on both the pressure exerted on the blood and the diameter of the blood vessel. These two factors are not independent. As the total diameter decreases or increases then the pressure varies inversely. In other words, if diameter decreases then pressure increases. Pressure is also affected by heart rate. The faster the heart pumps, the more blood moves through it, the greater the pressure.

View the animation below, then complete the quiz to test your knowledge of the concept.






1Which of the following statements is true concerning blood vessels?
A)the difference in the volume per minute of the blood in the capillaries is equal to the volume per minute in the artery that feeds them.
B)the sum of the velocity of the blood in the capillaries is equal to the velocity in the artery that empties into them.
C)the sum of the volume per minute of the blood in the capillaries is equal to the volume per minute in the artery that feeds them.
D)the distance moved per minute by the blood in the capillaries is equal to the distance moved per minute by the artery that empties into them.
E)the sum of the friction along the walls of capillaries is equal to the friction along the walls of the artery that feeds into them.



2Which of the following statements is not true concerning blood vessels?
A)as vessel size decreases in cross section, friction increases.
B)as vessel size decreases in cross section, volume increases.
C)as vessel size decreases in cross section, velocity decreases.
D)as vessel size decreases in cross section, pressure increases.
E)as vessel size decreases in cross section, flow decreases.



3Blood flow is...
A)inversely proportional to the cross section of the blood vessel.
B)directly proportional to the cross section of the blood vessel.
C)inversely proportional to the cross section of the blood vessel.
D)inversely proportional to the velocity of the blood vessel.
E)directly proportional to the velocity of the blood vessel.



4The sum of the blood velocity of arterioles is equal to the blood velocity of the artery that feeds them.
A)True
B)False



5Arteries branch into narrower blood vessels called arterioles.
A)True
B)False







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